Question
I own a seven-year-old Dutch Warmblood gelding that weighs about 1,270 lb (575 kg). He’s ridden five or six days a week in lower-level dressage. He is allowed four hours per day on medium-quality pasture, and the rest of his day is spent in a stall. He’s fed six to eight flakes of hay and three pounds (1.4 kg) of a low-starch feed per day. He also gets supplements for joint and hoof health. He has intermittent lameness that is usually short duration (a few days) but recurs about once a month. A full lameness workup revealed chronic pedal osteitis. Is it possible he was not getting enough calcium or the wrong ratio of calcium to phosphorus due to feeding him below the recommended daily allowance of the concentrate? He is a fairly easy keeper. At one point, I fed him a calming supplement that is high in magnesium. Could that throw his calcium level off? He’s a young horse with bone loss in that foot. Can I correct it with feed and rest? Can I give him a calcium supplement? What can I do to test his levels? Hair analysis?
Answer
You presented several questions in your note to me. I will try to answer each one individually.
Question: Was my gelding not getting enough calcium or the wrong ratio of calcium to phosphorus due to feeding him below the recommended daily allowance of concentrate?
Answer: It is really difficult to say if there was a calcium problem without more information on the hay because that is the major source of calcium in the diet. If there is any alfalfa in the hay, the chances of low calcium are not likely because of the high levels of calcium in alfalfa (lucerne). With so little feed, it was definitely not contributing any major amounts of calcium to the diet. I rarely come across calcium deficiency in this country but occasionally come across hay analyses that have reversed calcium:phosphorus ratios (more phosphorus than calcium). Having a reversed calcium:phosphorus ratio can cause problems like nutritional secondary hyperparathyroidism (big head disease). Lameness is one of the symptoms. This disease is much more common in parts of the world where there are oxalates in the grass (hay) that make the calcium present unavailable to the horse. In this country, the average calcium/phosphorus/magnesium amounts and ranges in grass hay from the forage testing lab Equi-analytical.com are:
% calcium: 0.512, range 0.278-0.745
% phosphorus: 0.240, range 0.147-0.333
% magnesium: 0.205, range 0.125-0.285
As you can see, there would not normally be a problem with calcium unless it is compromised in the hay. The ideal calcium:phosphorus ratio is 2:1 but can range anywhere from 1.1:1 to 6:1 with no problems in adult horses.
Question: He is a fairly easy keeper. At one point, I fed him a calming supplement that is high in magnesium. Could that throw his calcium level off?
Answer: The supplement you fed has 1 g magnesium and 0.6 g calcium, which is not balanced. However, this is not normally a problem if there is enough calcium in the hay. The ideal ratio of calcium to magnesium is 3:1. A typical diet of 22 lb (10 kg) of hay with a calcium content of 0.5% would supply 50 g of calcium and 20 g of magnesium, so you can see that 1 extra g of magnesium will not normally interfere with the calcium balance.
Question: He’s a young horse with bone loss in that foot. Can I correct it with feed and rest?
Answer: Bone loss in one foot is not usually indicative of a problem with the diet. If the diet were to blame, more bones would be affected. Regardless, giving him a balanced diet is always recommended. You have the right idea with switching to a feed with a recommended feeding rate that more closely matches the caloric needs of the horse. If you are interested in reducing the feed intake, you could try a ration balancer, which will have a recommended intake of 1-2 lb (0.5-1 kg) per day. An example of a ration balancer is All-Phase. It will balance out the calcium and phosphorus content in the diet for almost any hay, as well as supplying all of the other nutrients that may be lacking from feeding under the recommended feeding rate of a feed. Pedal osteitis is usually caused by a musculoskeletal problem affecting the foot. Consult with your veterinarian about corrective shoeing, anti-inflammatories, or other drugs that may help to reduce bone loss or promote mineralization of the coffin bone.
Question: What can I do to test his levels? Hair analysis?
Answer: Unfortunately, there is little you can do to get a reliable test result because of the body’s homeostatic regulation of macrominerals. Blood tests don’t really tell anything unless the horse is severely deficient in calcium because the body tries to maintain the blood calcium at a certain level, so it is releasing calcium from the bone or storing it or excreting it in order to maintain that level. Hair is notoriously unreliable for looking at body levels of minerals, except the heavy metals. For minerals like calcium, the best way to determine if there is a deficiency is a diet analysis.
Question: Can I give him a calcium supplement?
Answer: You can supplement with a balanced bone supplement, like DuraPlex (not available in Australasia), which has been shown to improve bone density in horses that are stall bound and do not have regular concussion on the bones that helps to maintain bone strength.
